Here are some settings that are recommended for most players. If you use cMod, these settings should already be set by default, but they may need to be set manually in other clients.

com_maxfps 125
Due to quirks in the EF physics engine, this is needed for optimal speed and jump height on some servers. It can also make the game run more smoothly compared to lower values.

com_hunkmegs 256
Required for some maps.

r_mode -1
r_customWidth x
r_customHeight y
Enables custom screen resolution mode, where x and y should generally be the native resolution of your monitor if you use fullscreen mode. For example, if your monitor runs at 1920x1080, r_customWidth would be 1920 and r_customHeight would be 1080.

r_picmip 0
r_ext_textureFilterAnisotropic 1
r_ext_max_anisotropy 16
Additional graphical improvements, but which could come at the expense of framerate on some computers.

rate 100000
snaps 100
Improves network performance by ensuring server-to-client frames are not deferred due to rate limiting. Appropriate for most connections faster than dialup.

cl_maxpackets 125
Improves network performance by increasing the rate of client-to-server command updates. Appropriate for most connections faster than dialup.

Other Settings

Here are some other settings that may be useful for configuring EF.

sensitivity
Used to fine tune mouse sensitivity. Default is 5. Decimal values are allowed.

cg_fov
Default is 80, but higher values can be used to widen view area.

cg_crosshairSize
Default is 24. Lower values make the crosshair smaller.

cg_drawTimer
Set to 1 to enable displaying the time remaining in the match.

cg_drawFPS
Set to 1 to enable displaying the current framerate.

in_mouse
If you are troubleshooting mouse (and sometimes keyboard) related issues, try setting this to both -1 and 1. It requires a full restart of EF for either value to take effect.

r_gamma
This is the main setting to control the brightness of the game. Typical values range from 1.0 (dark) to 2.0 (bright). However, this setting is very prone to compatibility issues. For best results use the cMod client.

r_ignoreHWGamma
Set to 1 to force a software approach to applying r_gamma, which can avoid compatibility problems, but may not be visually optimal. While this is set you will need to do a vid_restart for any r_gamma changes to take effect. The effectiveness of this option may vary between EF clients.

r_mapOverBrightBits
Default is 1; settings of 2 or 3 can make the game appear brighter or fix issues with some maps. However it can also mess up the colors on other maps, so I only recommend this as a last resort if you can't get the regular r_gamma settings to work.